USDA Hardiness Zone 7a
Frost Dates for 19380 — West Chester, Pennsylvania
NOAA 1991–2020 normals from W Chester 2 NW, PA (375 ft), 2 miles west.
Updated
In West Chester, the last spring frost (32°F) is around April 26 in half of years and has passed by May 11 in nine years out of ten. The first fall frost comes around October 18, as early as October 4 one year in ten, leaving a typical freeze-free season of 174 days (NOAA, W Chester 2 NW, PA).
- Last spring frost
- April 26
- First fall frost
- October 18
- Growing season
- 174 days
- Hardiness zone
- 7a
50% probability
50% probability
freeze-free, 50%
0 to 5°F (-17.8 to -15.0°C) coldest night
- First snow
- December 6
- Last snow
- March 24
- Winters with snow
- 100%
- Snow per year
- 28.4"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in West Chester
Half of springs at W Chester 2 NW, PA see their last 32°F night by April 26; only one in ten is past it by April 10, and one in ten still has one after May 11. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 6 20%, and after May 11 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 72% of the 176 Pennsylvania stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 18 in half of years, as early as October 4 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 12 days later, around October 30; in spring the one-in-ten date for 28°F is April 26, 15 days before the 32°F one. The freeze-free season lasts 174 days in a typical year, shorter than at 52% of the 176 Pennsylvania stations; it reaches 194 days one year in ten and falls short of 152 one year in ten. On average 131 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 11 days longer, to about May 7, and return around October 7. Severe cold of 16°F or below comes every winter, usually between December 6 and March 7.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 23 | Apr 28 | May 1 | May 4 | May 7 | May 10 | May 13 | May 18 | May 22 |
| 32°F | Apr 10 | Apr 16 | Apr 20 | Apr 23 | Apr 26 | Apr 29 | May 2 | May 6 | May 11 |
| 28°F | Mar 28 | Apr 1 | Apr 5 | Apr 8 | Apr 11 | Apr 15 | Apr 18 | Apr 22 | Apr 26 |
| 24°F | Mar 15 | Mar 20 | Mar 25 | Mar 28 | Mar 31 | Apr 2 | Apr 5 | Apr 8 | Apr 15 |
| 20°F | Mar 1 | Mar 8 | Mar 12 | Mar 15 | Mar 18 | Mar 22 | Mar 26 | Mar 30 | Apr 3 |
| 16°F | Feb 18 | Feb 25 | Feb 28 | Mar 3 | Mar 7 | Mar 10 | Mar 13 | Mar 17 | Mar 22 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 27 | Oct 1 | Oct 3 | Oct 5 | Oct 7 | Oct 9 | Oct 12 | Oct 17 | Oct 22 |
| 32°F | Oct 4 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 24 | Oct 28 | Nov 1 |
| 28°F | Oct 14 | Oct 19 | Oct 24 | Oct 27 | Oct 30 | Nov 1 | Nov 3 | Nov 6 | Nov 11 |
| 24°F | Oct 29 | Nov 1 | Nov 4 | Nov 6 | Nov 8 | Nov 11 | Nov 14 | Nov 18 | Nov 24 |
| 20°F | Nov 7 | Nov 11 | Nov 14 | Nov 19 | Nov 22 | Nov 24 | Nov 29 | Dec 3 | Dec 9 |
| 16°F | Nov 17 | Nov 23 | Nov 28 | Dec 2 | Dec 6 | Dec 9 | Dec 14 | Dec 20 | Dec 28 |
Freeze probabilities 1991–2020 at W Chester 2 NW, PA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 19380 →Compare West Chester with another place →
Weather by month in West Chester
July is the warmest month at W Chester 2 NW, PA, averaging 86°F by day and 64°F at night; January is the coldest at 40°F and 20°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 35% of years.
Warmth for growing adds up to 3,270 growing degree days a year (base 50°F), more than at 77% of the 176 Pennsylvania stations. 34% of them (1,098) have built up by the end of June, and July adds the most, 773. Precipitation totals 51.0 inches a year, most in September (5.7") and least in February (3.1"); May to September bring 45% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 40 | 20 | 3.7 | 100% | 27 | 1 |
| Feb | 43 | 21 | 3.1 | 100% | 25 | 3 |
| Mar | 51 | 29 | 4.6 | 100% | 21 | 21 |
| Apr | 63 | 38 | 3.8 | 97% | 9 | 119 |
| May | 73 | 49 | 3.8 | 35% | 1 | 343 |
| Jun | 82 | 59 | 4.0 | 0% | 0 | 611 |
| Jul | 86 | 64 | 4.4 | 0% | 0 | 773 |
| Aug | 84 | 62 | 4.8 | 0% | 0 | 713 |
| Sep | 78 | 54 | 5.7 | 2% | <1 | 477 |
| Oct | 66 | 41 | 4.8 | 88% | 6 | 169 |
| Nov | 55 | 32 | 3.6 | 100% | 17 | 33 |
| Dec | 44 | 25 | 4.7 | 100% | 25 | 8 |
Monthly normals 1991–2020 at W Chester 2 NW, PA (375 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Phoenixville 1 E, PA, 11 miles northeast of West Chester and 290 feet lower, has a last frost 8 days earlier (April 18), a first frost 9 days later (October 27), a season 18 days longer.
When it snows in West Chester, Pennsylvania
The first measurable snow (0.1 inch or more) in West Chester usually arrives around December 6, and the last of the season around March 24. Those are the middle dates across the winters of 1991–2020 at Glenmoore, PA, 11.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 33 days after the last snow.
Planting calendar for 19380
| When | What to do |
|---|---|
| February 15 – March 1 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 1 – March 15 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 29 – April 12 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 26 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 26 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 4 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 18 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 19380 is 2 miles from W Chester 2 NW, PA, which stands at 375 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 19382 (West Chester). The 2023 USDA Plant Hardiness Zone Map lists ZIP 19380 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across Pennsylvania →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.